If this is only a temporary bug cause the git conatins some buggy
code...no problem.
If I did something wrong or be able to fix it I would like to know,
what goes wrong...?!?
How can I get/create this ".rel.plt" file ?

Try reverting to the version I used and then attempt to compile; the version you have may very well be broken especially since the author noted it was "testing". You'll have to read up on the basics of GIT.

My ineptitude with git did not allow me to modify my existing tree, so I started anew and downloaded a fresh image and configured and cross compiled it. It did not appear that the compile successfully ended; however, the u-boot was generated so I'm not arguing with success.

It's possible that before I had errors, but that the u-boot had been built so I ran with it discarding any concern for the fact that the make may not have successfully finished. Sloppy, but I moved forward.

At any rate, if you do not have u-boot, then kindly replicate what I just did using the Yanok version and paste-bin, then let's ask Mark Frysinger [Vapier] what he thinks we can do to ferret out the discrepancy. The cross compiler should give us the same error messages when run against the same source; that it does not merits investigation and possibly a bug.